Got my Iphone 5 yesterday. After hearing the other reports, I deleted the old profiles for my old phone and my Ipad before trying to pair my Iphone. It worked the first time no problem with my 2012 Impreza premium.
Before this I had been using my Ipad through the USB connector as my primary music/audio generator (that way I could keep my old phone linked through BT). So, I thought I'd try that with the Iphone 5. It almost worked, but not fully. It would bring up the song on the head unit screen, and it would show up on the iphone as a "dock", but it wouldn't auto play, and when I'd hit play on the screen it would play for a second then pause right away. I also couldn't navigate through my music collection like I could on the Ipad (still running old os).
Just thought I'd pass this info along, since I hadn't seen any one else mention the USB connection before. I was planning on running this through BT any way, so it's not a huge deal, just thought it was good info.